1. Field of the Invention
The present invention relates to data communication devices, and in particular to a wireless data communications system utilizing radio frequency identification technology.
2. Description of Related Art
In the automated identification and data capture industry, it is known to operate a wireless network that includes a plurality of terminals that communicate over a radio frequency (RF) channel with a host computer. The terminals may be portable, such as hand-held data-collection terminals and pagers, and generally include an input mechanism such as a keyboard for manual input of information or a scanner for reading barcode information. These terminals may be used in a variety of applications such as inventory control, shipping and receiving, and security management. In operation, each terminal communicates with the host computer over a conventional bi-directional radio system. A typical bi-directional radio is capable of receiving and transmitting RF signals in accordance with a selected RF protocol, such as polling or contention, which allows multiple terminals to communicate with the same host computer.
The use of a conventional bi-directional radio of these prior art systems has certain drawbacks. For example, the radio can be relatively expensive, especially in terminals designed for simple, short range wireless communication. Further, the terminal""s battery, in addition to powering the terminal""s data collection facilities, must also provide power sufficient to transmit and receive radio signals to and from the host computer, resulting in additional drain on the battery. A further drawback is that these radio systems often use a licensed frequency band requiring Federal Communications Commission (xe2x80x9cFCCxe2x80x9d) approval.
Accordingly, a low-cost wireless data communications system that avoids the drawbacks of conventional bi-directional radio systems would be desirable.
In accordance with the teachings of the present invention, a wireless data communications system includes at least one portable device, such as a wireless data collection terminal, which is equipped with a programmable RFID tag. Generally, an RFID tag is less expensive than a conventional bidirectional radio, will cause less battery drain, and typically operates in an unlicensed frequency band that does not require FCC approval. Thus, the portable device of the present invention avoids many of the drawbacks of conventional RF systems. In addition, each portable device may include an input device, such as a keyboard or barcode scanner, for collecting data, a memory for storing the collected data, and a display.
The wireless data communications system further includes at least one RFID interrogator connected to a host computer. In operation, the RFID interrogator polls for RFID tags, and when an RFID tag is detected, the data stored in the memory of the portable device may be uploaded to the RFID interrogator through the RFID tag. Likewise, data could be downloaded to the data collection terminal via the same RFID interrogator. The data downloaded to the portable device could include visual display data for use on the display of the portable device, audio data for playback over a speaker of the portable device, executable code to customize the processing logic of the portable device, data to be used in subsequent processing by the portable device, and other types of data.
In another embodiment, the location of each portable device in the wireless data communications system may be determined and tracked by a network of interrogators. Each interrogator has an associated operating range (xe2x80x9ccellxe2x80x9d) within which a data collection terminal may be interrogated, and the interrogators are positioned so that their respective cells provide adequate coverage of the area over which each portable device might move during communications. When a portable device is within a particular interrogator""s cell, a communications link between the interrogator and the portable device may be established. A search algorithm running on the host computer may be used to determine the cell location of the portable device and track the portable device""s movement through the cells of the covered area. In addition, the location of the portable device within each cell can also be determined by measuring the signal propagation delay between the portable device and each of three or more interrogators associated with neighboring cells. The location of the portable device can be used by the host computer to control access privileges for the portable device, to send messages to a user closest to a particular area, to select proprietary data for download at particular user locations, or for any other purpose in which location of the portable device or user may be desirable.